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This Week’s Discoveries | 20 March 2018

20 maart 2018
Niels Bohrweg 2
2333 CA Leiden

First Lecture

The noise of superconducting electrons

Koen Bastiaans (LION)
Koen is a PhD student in the  Milan Alan group at LION. The aim of Milans group is to explore and understand quantum materials, including strange metals, high-temperature superconductors, and quantum critical electron matter.

The charge transport between two weakly coupled superconductors is rather unique. While in the case of metals the transferred charge simply stems from tunnelling electrons, the transport in a superconductor-insulator-superconductor junction is much more diverse. At zero-bias, a pure dissipation-less current flows, carried by paired electrons, transporting twice the electron charge each. When a bias is applied various processes allow for transport of quasiparticles that can transfer multiples and/or fractions of elementary charge. I will present the developing of a noise-sensitive Scanning Tunneling Microscope to directly probe the effective charge that is transported in two weakly coupled superconductors. This opens a new route to study charge transport in quantum materials, like high-temperature superconductors.

Second Lecture, Lorentz Center highlight

Symmetric Cryptanalysis: the Foundation of Trust

Maria Naya Plasencia (Inria, France)
Maria is an member of the Security, Cryptology and Transmissions (SECRET) research team at Inria, the French National Institute for computer science and applied mathematics. The research work within the project-team is mostly devoted to the design and analysis of cryptographic algorithms, in the classical or in the quantum setting. It is especially motivated by the fact that the current situation of cryptography is rather fragile: many of the available symmetric and asymmetric primitives have been either threatened by recent progress in cryptanalysis or by the possible invention of a large quantum computer. Most of our work mixes fundamental aspects and practical aspects of information protection (cryptanalysis, design of algorithms, implementations). Maria is one of the participants in the workshop Flexible Symmetric Cryptography that is being held in the Lorentz Center from 19 March 2018 through 23 March 2018.

The security of asymmetric primitives typically relies on the hardness of a well-established mathematical problem and is then well accepted by the community. By contrast, the security of symmetric primitives is much less clearly established and the existing pseudo-security-proofs always rely on an ideal modelization that is far from realistic (for example, modeling a pseudo-random distribution by a truly random one). We are then often left with an empirical measure of the security, provided by a thorough, and even more importantly never-ending study of the symmetric primitives by cryptanalysts.
That is why confidence in symmetric primitives is always based on the amount of cryptanalysis they have received, and on the security margin that they have left. To react as quickly as possible when required, it is important to analyze the security thoroughly with respect to all currently available cryptanalysis tools (including quantum ones); and then keep it up to date as the tools evolve.

This Week's Discoveries

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